The underlying hypothesis of the LDRC is that the neurodevelopmental building blocks that support low level information processing (LLIP) are specifically disordered in learning disabled (LD) children. This condition results in a deficit in the normally rapid processing of temporal information. The primary goal of Project IV is to provide, using the tools that are unique to neurophysiology, an independent validation of the hypothesized differences in LLIP between children with learning disabilities and children without such disabilities. As part of a coordinated effort with the other projects in the LDRC, Project IV will evaluate 200 LD children and 200 children in the standardization sample who, as part of Project I, will be defined and sub- grouped based on profiles of strengths and deficits on "physiological- plausible" variables of temporal information processing in the auditory, visual, and motor sequencing domains. Project IV supports the basic premise of the LDRC as stated in the Overview, namely that learning disabilities represent a functional deficit. Project IV will rely on the quantification of EEG data which is sensitive to the temporal aspects of neural function to: 1) Derive neurophysiological measures of LLIP which are sensitive to temporal information processing in visual, auditory, and motor systems domains and which characterize learning disabilities. 2) Apply a standard neurophysiological test battery which has been used to differentiate LD from normal children and to develop based upon this battery basis neurophysiologic measures of processing including cortical- cortical connectivity, spectral coherence; processing speed and efficiency, evoked potential latency; and source and number of EP generators, Brain Electrical Source Localization (BESA).